Facsimile transmitter



Sept. 13, 1932. H, M ELSEY ET AL v 1,877,566

FACSIMILE TRANSMITTER Filed 001?. 6. 1930 fiaward/W. E/se AfTORNEY Patented Sept. 13, 1932 I /ST TES HOWARD M; ELSEY, or OAKMONT,3AND..'LA viirmn n. PHILPOTT, o fwrn INsBURG,

P NNSY ANIA, ASSIGIN'ORS To wnsrnvenousn ELECTRIC, Aim manurao'runinq COMPANY, A CORPORATION or. rENns Lv NIA i rncsrirrLE statesmen Application iiiea October 6, 1930. Serial ,No. 486,662l

Our invention relates to the transmission of pictures, 1mages,pr1nted matter orthe like wherein a'beam of light is caused to traverse successive elements of a subject, the

' resultant light variations being subsequently translated into corresponding electric cur rents for transmissionover wires or through the ether.

'More particularly, our invention relates to improvements in chopper mechanism nor-' mally used in facsimiletransmission systems.

A general layout of facsimile-transmission systems, according to the prior art, comprises a source of lightfor the purpose of producing a light beam with which to scan a picture or view to betransmittech The dimensions of the beam are controlled by a mask surrounding or enclosing said light source, a slit or other small opening in said mask determining the physical dimensions of said beam. A chopper mechanism, comprising means for interrupting said light beam at an audio-frequency rate of approximately 2000 interruptions per second, is inserted in the path of the beam.

This chopper mechanism, as disclosed by the prior art, usually takes the form of a disc having a plurality of light passages dispersed about its circumference. The interrupted light beam is condensed or focused upon the picture or subject to be transmitted, the picture or subject being so moved with respect to the beam as to cause the interrupted light beam to scan all the elements of the picture. The light, as affected by the picture elements, is subsequently translated into corresponding electric currents and transmitted in this form. At the receiving end, the process is substantially reversed to reproduce the transmitted picture.

Were no chopper mechanism to be used, the current in the photo-cell circuits would, accordingly, be modulated only by the variations in the intensity of the various picture elements, the frequency of the currents being either below the range of audio-frequency or of a frequency close to the lower limit of audio-frequencies. Currents of such low frequencies cannot be efiiciently amplified by any known amplifying means. The purpose of the chopperumeclianism, therefore, is;

the source of light iszsubstantially totally cn-- closed,the intensity of the sou'rce is limited because of'the heat generated by it in the limited space-bounded-bythe mask.

According to our invention, we are enabled to utilize. a very intensesource of light. WVe accomplish the above result, broadly, by controlling the temperature of the medium about the source of energy. Y It is,accordingly, one object of our invention to provide means, in facsimile transmitters,'whereby it becomes possible to generate abeam of energy of great intensity for scanmng purposes, i

Another object of our-invention is to pro vide a choppermechanism fora facsimile so; i

transmitter which is adapted .to function'as a cooling agentfora light-ray-generating source. I. 1

Anotherobject. of our invention is to provide means for causing, circulation of} air about heatedportions of a facsimile transmitter. I

.Additional objects of our invention will be pointed out in detail in the following description, taken in conjunction with the accompanying drawing wherein: v

Figure 1 is a plan viewof a facsimile transmitter embodying ourimprovements.

. Fig; 2 is a view, in cross section, of the choppermechanism along the plane IIII ofFigQL Referring more particularly to the draw ing, the transmitter comprises, in general, a source of light energy-,a chopper mechanism, indicated broadly by reference numeral 3, a

and is focused upon a: view 1 3-to be transmitlight ray;

ted. The view"- is supported or wrapped about the rotatable support or cylinder 5" which, in addition to its movement of rotat1on,' 1s also caused to assume a translatory 1 otion. With a stationary beam of light ocused upon the picture 13, the movement of the picture relative thereto will thereby ause the beam to scan the entire picture. The light reflected from. the picture willbe modified or modulated by the various picture elements scanned. This reflected light is caused to fall upon or strike the cathodesof the pair of photosensitive devices 7 located in close proximity to the pictureand adja- Q? cent to the light ray. The efiect of the reflected light upon the-photosensitive devices will be to modulate current in the photosensitive device circuits in-a: manner which will closely simulate the modulations of the- Referring more particularly to." ourimproved chopper mechanism,;itf takes the form of. an element 1550f canrshape openiat' one end and mounted on a" shaft 11 at. the other. end,

whereby the chopper may be rotated at any low for circulation of air.

the cylindrical surface ofwthe chopper, we-

desired speed; The chopper. element is slipped over 311(15811610568 the lightvsource- 1 and its protecting n1 ask11',.suflicient space being provided between saidelements to al- Iprovide a plurality of slots 19, the distance etween said slots being sufiicient to cover the slit or'opening 9 in the mask, whereby the X ray of light passing; through said slit may will be of much greater va'1ue,resultingin a be efiectively interrupted at a frequency which will be determined by the number of such slots in the chopper mechanism, and

the speed of rotation of thesame.

Because of the particular construction of our chopper apparatus, a fan action will be obtained during its operation and, since the mask is substantially unobstructed or opened:

at bothends, except for a light-source sup "porting element (not shown) within one end,

a path is provided for the circulation of air about the source, of light. The rotation of the rotating chopper member will cause'the heated air to be drawn through one end of the mask, this air being replaced by an in rush of cooler air through the other end of the mask, thereby providing a constant cooling effect upon the source of light energy. Because of this improved result, as obtained by our chopper device, we are enabled" to make useof a source of light of great intensity, with the ultimate result that the intensity of the light beam striking the'picture app ded: claim,

Dispersed about.

erful effect maybe producedon the enclosed air." Therefore, while wehave disclosedour invention in great detail, we do'not desire to .belimitedto. such except insofar as is necessitatedt 'the prior art and the spirit oi the We claim as our invention:

In a view-transmission system, a source of energy, anopen ended masking element for said source providedwith a slit for; producing; a ray, and means associated therewith for interrupting said ray, said means comprising an element substantially enclosing said source of energy and said mask and provided with a plurality of openings where-' by said ray of light may be interrupted by movement of said element relative to said source of energy.

In testimony whereof, we have hereunto subscribed our names this 30th day of September, 1930. v

' ,HOWARD M. ELSEY.

7 LA VERNE R. PHILPOTT. 

